The mobile communication system has evolved into a high-speed, high-quality wireless packet data communication system to provide data services and multimedia services beyond the early voice-oriented services. Recently, various mobile communication standards, such as High Speed Downlink Packet Access (HSDPA) and High Speed Uplink Packet Access (HSUPA), Long Term Evolution (LTE), and Long Term Evolution-Advanced (LTE-A), which are defined in the 3rd Generation Partnership Project (3GPP), High Rate Packet Data (HRPD) as defined in the 3rd Generation Partnership Project-2 (3GPP2), and Institute of Electrical and Electronics Engineers (IEEE) 802.16, have been developed to support the high-speed, high-quality wireless packet data communication services. Especially, an LTE system, which is a system developed in order to efficiently support high speed wireless packet data transmission, uses various wireless access technologies to maximize the wireless system capacity. An LTE-A system corresponds to an advanced wireless system development of the LTE system and has an improved data transmission capacity in comparison with the LTE system.
In general, the term LTE refers to evolved Node B (eNB) and User Equipment (UE) apparatuses corresponding to Release 8 or 9 of the 3GPP standard organization and the LTE-A refers to eNB and UE apparatuses corresponding to Release 10 of the 3GPP standard organization. The 3GPP standard organization has standardized the LTE-A system and is now developing a standardization of a subsequent Release having improved performance based on the standardized LTE-A system.
Existing 3rd Generation and 4th Generation wireless packet data communication systems such as HSDPA, HSUPA, HRPD, LTE/LTE-A, use an Adaptive Modulation and Coding (AMC) scheme and a channel-sensitive scheduling scheme to improve transmission efficiency. With the use of the AMC method, a transmitter can adjust the amount of transmission data according to the channel state. That is, when the channel state is poor, the transmitter reduces the amount of transmission data to adjust the reception error rate to a desired level, and when the channel state is good, the transmitter increases the amount of transmission data to adjust the reception error rate to the desired level and to efficiently transmit a large volume of information.
With the use of the channel-sensitive scheduling-based resource management method, the transmitter selectively provides a service to a user having a good channel state among a plurality of users, thus increasing the system capacity compared to the method of assigning a channel to one user and providing a service to the user with the assigned channel. Such a capacity increase as in the above description is referred to as “multi-user diversity gain”. In summary, the AMC method and the channel-sensitive scheduling method each are a method of applying the appropriate modulation and coding techniques at the most efficient time determined according to the partial channel state information fed back from a receiver.
The AMC scheme, when used together with a Multiple Input Multiple Output (MIMO) transmission scheme, may include a function of determining the rank or the number of spatial layers of a transmission signal. In this event, the AMC scheme determines an optimal data rate in consideration of the number of layers for transmission using MIMO as well as a code rate and a modulation scheme.
The MIMO transmission scheme using a plurality of transmission antennas for transmission of wireless signals is divided into Single User-MIMO (SU-MIMO) for transmission to one UE and Multiple User-MIMO (MU-MIMO) for transmission to a plurality of UEs using identical time and frequency resources. In the case of SU-MIMO, a plurality of transmission antennas transmit wireless signals to a plurality of spatial layers for one receiver. In this event, the receiver requires a plurality of reception antennas, in order to support the plurality of spatial layers. In contrast, in the case of MU-MIMO, a plurality of transmission antennas transmit wireless signals to a plurality of spatial layers for a plurality of receivers. The MU-MIMO is more advantageous than the SU-MIMO in that the MU-MIMO does not require a receiver to be equipped with a plurality of reception antennas. However, the MU-MIMO is disadvantageous in that, since wireless signals are transmitted to a plurality of receivers through the same frequency and time resource, interference may occur between the wireless signals for different receivers.
The LTE and LTE-A have employed various standard technologies for supporting Coordinated Multi-Point Transmission and Reception (CoMP), which is a cooperative communication, in order to control the interference. Further, there is a method in the related art in which a UE performs interference management. In order for a UE to perform interference management, it is necessary to accurately measure information, such as reception intensity and channel, of each interference signal.
The above information is presented as background information only to assist with an understanding of the present disclosure. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art with regard to the present disclosure.